1. Field of the Invention
The invention relates to slurry supply, and in particular to a slurry dispensing system with dual loop for non-stop supply during flushing.
2. Description of the Related Art
FIG. 1 depicts a conventional slurry supply system comprising a supply unit 100, a slurry loop A and a slurry loop B. The supply unit 100 comprises a station A and a station B. The station A and station B have the same structure. The station A comprises a tank 10, a pump 20, and valves 30, 40 and 50. The station A and station B are serially connected by loop A. The loop B is connected to loop A via valves 140 and 240. As slurry is expended during chemical flushing, slurry supply is switched to the station B after a predetermined operating period of the station A, whereby the station A is replenished with new slurry. When slurry is supplied from the station A, the valves 30, 40 in the station A and the valve 50′ in the station B are opened. Slurry runs in loop A via pressure control units 200 to provide slurry for a plurality of points of use 500 (FIG. 1 shows only one) by opening the valves 120 and 220. When loop A is to be maintained, such as cleaning or washing, the valves 120 and 220 are closed and the valve 240 is opened, whereby slurry runs in loop B. The valve 140 is not opened until the slurry in the loop B reaches a stable state, normally taking several hours to one day to achieve a stable state, during which points of use 500 are idle while awaiting slurry supply, reducing manufacturing efficiency.